International Orthopaedics (SICOT) DOI 10.1007/s00264-015-2786-7
ORIGINAL PAPER
Short-term outcomes of robotically assisted patello-femoral arthroplasty Ugur Turktas 1 & Ahmet Piskin 2 & Gary G. Poehling 3
Received: 31 January 2015 / Accepted: 4 April 2015 # SICOT aisbl 2015
Abstract Purpose The purpose of this study was to determine the outcomes in patients treated with robotically assisted patellofemoral arthroplasty (PFA). Methods This technique offers a safe, reliable, and reproducible way of obtaining correct implant positioning in patello-femoral arthroplasty, and as a result, reduces revision surgery due to implant malalignment. We evaluated 30 knees in 29 patients who underwent robotically assisted patello-femoral arthroplasty between June 2009 and May 2011. Mean follow-up was 15.9 months. This was a retrospective study that involved chart reviews and radiographic analysis. Radiographic analysis included preoperative and postoperative plain films for implant positioning. Functional outcomes were evaluated using the Oxford Knee Score (OKS), range of motion, University of California at Los Angeles (UCLA) patient activity-level ratings, visual analog pain scale (VAS), and the Knee Society Score (KSS). Results The patients had an average OKS of 21.7 preoperatively and reached an average of 33.5 postoperatively (p = 0.0033). Pre-operative UCLA patient activity-level ratings was 3.1, compared with 4.8 postoperatively. Average VAS preoperatively was 8 and postoperatively it decreased to 2.1 (p = 0.0033). The average KSS final score pre-operatively
* Ugur Turktas [email protected] 1
Department of Orthopaedics and Traumatology, Turgut Ozal University School of Medicine, Ankara, Turkey
2
Department of Orthopaedics and Traumatology, Ondokuzmayis University School of Medicine, Samsun, Turkey
3
Department of Orthopaedic Surgery, Wake Forest University School of Medicine, Winston-Salem, NC, USA
was 56 and postoperatively it increased to 68.3 while the functional score pre-operatively was 47.2 compared to 68.1 postoperatively (p = 0.011). As a result, patello-femoral arthroplasty is an emerging knee resurfacing technique that is an alternative to the total knee arthroplasty. Conclusions The early retrospective data for roboticallyassisted PFA show encouraging results. Advantages of this technique include a smaller incision, faster rehabilitation, preservation of bone stock, and implantation without malalignment. Keywords Patello-femoral . Arthroplasty . Robotically controlled . Robot assisted . Osteoarthritis
Introduction Isolated patello-femoral osteoarthritis (PFOA) is a common disease. Approximately 10–15 % of patients who have knee pain manifest pathology consistent with PFOA. In a radiologic study of 206 knees in 174 consecutive orthopedic outpatients, Davies et al. [1] reported that the incidence of isolated PFOA is 13.6 % in women and 15.4 % in men older than age 60. The patients had anterior knee pain, particularly upon standing up from a chair or climbing stairs. There are multiple options for this disease if conservative treatment fails. These include arthroscopic debridement, patellectomy, chondroplasty, tibial tubercle transfer, total knee arthroplasty (TKA), and patellofemoral arthroplasty (PFA). Patellectomy was a more common treatment in the past, but long term results were poor [2]. Many orthopedic surgeons prefer TKA for advanced PFOA, and this treatment gives predictably good results [3]. However, PFA has become increasingly popular as it has the advantages of preserving the unaffected parts of knee, is less invasive than primary TKA, and may allow more rapid
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recovery [4]. Recent studies have shown better results with PFA as a result of improvements in the design and manufacturing of implants, better patient selection and an appreciation of the need to balance the soft tissue [5]. Cartier et al. [6] reported excellent functional outcomes in 77 % of patients at a mean follow-up of ten years. In these cases, patients should be selected carefully to ensure that there is not co-existent tibio-femoral arthritis. The most common cause of failure is progression of osteoarthritis in the tibio-femoral compartments [5, 7]. However, the association of a PFOA and unicompartmental (medial or lateral tibiofemoral compartment) knee osteoarthritis (UKOA) is commonly seen and is known as bi-unicompartmental osteoarthritis (biUKOA). In these patients, bi-unicompartmental knee a r t h r o p l a s t y ( P FA p l u s e i t h e r m e d i a l o r l a t e r a l unicompartmental arthroplasty, also referred to as bi-UKA) can be performed. Recent literature indicates satisfactory outcomes of this surgical procedure. Heyse et al. [8] reported high satisfaction at 12 years in patients that had bi-UKA, suggesting that this procedure can be successful in preventing TKA in mid- to long-term follow-up. Bi-UKA is particularly preferred in young and active patients who have PFOA and UKOA [9]. PFA utilizing conventional techniques has some complications, such as patellar catching, snapping, and implant malalignment. The purpose of our study is to report our short-term results of PFA using robotic arm assistance. Our hypothesis is that this robotic technique has the ability to produce a safe, reliable, and reproducible way of obtaining optimized component position and alignment, which will improve the clinical outcome as measured by the Oxford score.
Patients and methods Between June 2009 and May 2011, 30 consecutive PFAs with robotic arm assistance were performed in 29 patients with isolated PFOA or bi-UKOA. Of the 30 arthroplasties (14 right knee and 16 left knee), 13 patients received only a PFA, 17 patients had bi-UKA performed. Of the patients who had biUKA, all but one underwent the arthroplasty at the time of the index procedure. That individual had a medial UKA two years prior to an ipsilateral PFA. The average patient age was 66.4 years (range 37–83 years). There were ten men and 19 women. Average body mass index (BMI) was 32.4. In general, patients remained in the hospital only one night after surgery, except for one patient who had difficulty walking. The average length of hospital stay was 1.25 days. Indications for surgery including anterior knee pain when getting up from a seated position and going up or downstairs. Each operation was carried out by or under the direct supervision of the senior author (G.G.P.). All included patients suffered from PFOA or PFOA and medial or lateral tibiofemoral compartment osteoarthritis with obvious clinical and radiological findings. In bi-
UKAs, the tibiofemoral implants were placed laterally in four cases and medially in 13 cases. Patients were followed regularly with clinical and radiographic examinations. This retrospective study involved chart reviews and radiographic analysis. The patient information gathered from the chart review included age, gender, body mass index, diagnosis, length of hospital stay, co-morbidities and previous surgeries. Radiographic analysis was evaluated pre-operatively, postoperatively, and at every follow-up with weight-bearing anteroposterior, lateral, and sunrise views. We classified each patient pre-operatively using the Kellgren and Lawrance osteoarthritis scale on the anteroposterior views. Functional outcomes were evaluated using Oxford Knee Sore (OKS), range of motion (ROM), University of California at Los Angeles (UCLA) patient activity-level ratings, visual analog pain scale (VAS), and Knee Society Score (KSS). We used the modified method of calculating the OKS from 0 (worst outcome) to 48 (best outcome) to allow for comparison. Functional data were gathered at the pre-operative assessment and again at the six, 12-, and 24-month follow-ups. Only patients who had PFA with minimum six month follow-up were accepted into the study. Specifically, we evaluated the outcomes of PFA. The patients who were scheduled to have robotically assisted arthroplasty underwent multislice computerized tomography of the operative knee, and these images were used for pre-operative planning and registering. The computer within the robot used these data during surgery to display a three-dimensional reconstruction of the knee. We first registered the femur and then marked the level of the cartilage at the interface margins to help insure smooth transition. Then the position of the implant was manipulated on the computer to insure ideal conditions and smooth transitions. The surgeon performed the operation with assistance from the robot utilizing the three-dimensional reconstruction. Robotically-assisted PFA or bi-UKA requires about a 12-cm mid-patellar incision. The patellar articular surface was cut by an oscillating saw with a guide apparatus and while the trochlear area was carved by a high-speed burr on the robotic arm. The femoral condyle and tibial plateau were prepared in a similar fashion, utilizing the burr attached to the robotic arm to prepare the areas to accept the implants. With this particular system, the patellar and tibial inlay implants are both polyethylene, while the femoral implants are a chrome-cobalt material. Quicksetting methacrylate-based bone cement was used for cementation. Patients with obvious patellar maltracking underwent lateral release. The patients were allowed to fully weight-bear the follow day under the control of a physiotherapist. Generally, patients start physiotherapy two weeks after surgery and in progress for four to six weeks, two or three times a week. Average physiotherapy time was six weeks (two to 20 weeks).
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Statistical analysis For analysis we used the Wilcoxon (the non-parametric and two-sample test) test in SPSS 15 (SPSS, Chicago, IL).
Results We assessed 30 knees in 29 patients who had PFA or bi-UKA. Average follow-up was 15.9 months (seven to 30 months). All included patients suffered from PFOA or multicompartment osteoarthritis with obvious clinical and radiological findings. All patients had conservative treatment before the surgery, ten patients had a surgical procedure performed prior to PFA. Nine of these patients had arthroscopic knee surgery and one patient had it twice. Another patient had a medial compartmental UKA. One patient had a lateral tibial plateau fracture during the operation and received a lateral buttress plate for fixation. Thirty consecutive knees with patello-femoral arthritis patello-femoral arthroplasty proved to be ineffective treatment, three patients needed further arthroscopic debridement and only one patient had revision TKA after bicompartmental UKA for persistent pain and swelling, no patients had loosening of the implants. Two patients had arthrofibrosis, defined as having less than 90° of flexion, and one of them had manipulation under general anesthesia. Only one patient had an infection and it was treated with an open debridement, irrigation, and manipulation. One patient had persistent drainage and underwent arthroscopic debridement. One patient had a deep venous thrombosis 1 year after the surgery. One patient had a distal-third femoral stress fracture nine months after PFA, which went on to intramedullary nailing. The patients were evaluated with the Kellgren and Lawrance osteoarthritis scale. Patients had an average of 3.7 on the scale; only three joints had grade 2 osteoarthritis and eight joints had grade 3. Average ROM improved from 115° pre-operatively (90– 130°) to 123° postoperatively (110–130°), an overall average increase of 6.9 %. All patients who did not have a complication reached full ROM in 9.2 (two to 24) weeks on average. Only 30 % of all patients who had bi-UKA reached their full ROM before the 10th week, while 84.6 % of all patients who had PFA reached their full ROM before the tenth week. This result shows that rehabilitation after PFA is easier than bi-UKA rehabilitation and the patients who had PFA can reach a full ROM earlier than patients who had bi-UKA. There was not a distinct difference when BMI was taken into consideration. The patients had an average OKS of 21.7 (range 10–37) pre-operatively and reached an average of 33.5 (range 12–47) postoperatively (p = 0.0033) (Fig. 1). Pre-operative UCLA patient activity-level ratings was 3.1, compared with 4.8 postoperatively. Average VAS pre-operatively was 8 and postoperatively it decreased to 2.1 (p = 0.0033) (Fig. 2). The average
Fig. 1 OKS and KSS outcomes. Statistically significant improvements were observed in postoperative OKS and KSS outcomes (*p = 0.0033, **p = 0.011)
KSS final score pre-operatively was 56 (range 41–78) and postoperatively it increased to 68.3 (range 10–95), while the functional score pre-operatively was 47.2 (range 5–80) compared with 68.1 postoperatively (range 20–100) ( = 0.011). Robotically assisted patello-femoral arthroplasty demonstrated good or excellent results based on the OKS in 54.3 % at a minimum one year follow-up (Figs. 3, 4, 5 and 6).
Discussion We found that PFA was a very effective treatment for PFOA. The patients who had PFA or bi-UKA had very good results and this was particularly true for active patients. The goals of performing compartment-specific arthroplasty were to preserve the intact ligaments, maintain bone stock, and avoid replacing the unaffected compartments of knee. Similarly, we aimed to minimize our incision, allow easier rehabilitation, and return patients to their prior level of activity. Consequently, anterior knee pain, which is one of the most common causes of knee pain, is reduced [10–12]. Specifically, we used the robotically assisted PFA as a treatment for PFOA. Pre-operative planning with computed tomography and intraoperative registration allow for the correct positioning of the components. Even though TKA is commonly preferred in patients who have PFOA, we feel that robotically assisted, selective arthroplasty is not only less invasive, it also allows for faster rehabilitation then TKA [13]. Earlier PFA designs had less than optimal clinical results [5, 14], but more recent
Fig. 2 Pre-operative and postoperative VAS scores. Postoperatively the VAS scores were significantly decreased (*p = 0.0033). Before surgery the patients had significant knee pain; after surgery this pain primarily ended
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Fig. 5 Patello-femoral and medial tibiofemoral compartment OA view
Fig. 3 Knee sunrise, anteroposterior and lateral view, the lateral compartment is well preserved, however the patello-femoral and medial compartments demonstrate severe arthritis
same time, we performed robotically controlled arthroplasty to the other compartment of knee which had OA. We evaluated short-term outcomes of robotically controlled PFA or biUKA.
designs have been shown to be more successful [15]. At the
Fig. 4 Bi-UKA patello-femoral and medial femoral components. The articular defects of the trochlea and the medial femoral condyle are covered by the prosthesis. Note the smooth transition between the two components
Fig. 6 Operated knee anteroposterior-lateral-sunrise view, the medial compartment and patello-femoral compartment have been replaced and the lateral compartment has been preserved. The balance of the knee has been restored
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Scheurer et al. [16] reported that secondary patellar resurfacing led to patient satisfaction in 57 patients with persistent anterior knee pain following TKA. Seventy-four percent of patients were satisfied. Panni et al. [17] reported that when complications of the resurfaced patella occur, they can be potentially catastrophic events. PFA complications are different from secondary patellar resurfacing and re-operation after patellar resurfacing. Malalignment, related to the prosthesis design, was the most common reason for the failure of first-generation prostheses [7, 18–22]. Van Jonbergen et al. [21] reported that optimal positioning was determined by visual alignment of the long axis of the trial component with the trochlear groove. The same study reported that the revision rate for malposition was 7 %. Van Wagenberg et al. [23] reported that patient outcomes were far from satisfactory, even after revision to a TKA. Our work did not see any malalignment or maltracking. We feel that pre-operative planning with computed tomography and intraoperative registration help to prevent malalignment. Another common reason for revision is progression of tibio-femoral osteoarthritis [7, 21]. Our ability to evaluate this in our patient population was limited by our relatively shortterm analysis. Nevertheless, we did not observe any progression of tibio-femoral osteoarthritis. We evaluated the pre-operative and postoperative ROM. We observed that the patients average ROM increased from 115 to 123°. The patients who did not have a complication reached their full ROM in 9.2 weeks on average. Other recent studies reported similar results. Heyse et al. [8] reported that ROM improved from 107 to 121.1°, and Odumenya et al. [24] reported that the median range of movement pre-operatively was 120° and postoperatively was also 120°. The OKS and KSS for these patients were also very encouraging. On average, the postoperative OKS score was 33.5 compared with a pre-operative score of 21.7. Odumenya et al. [24] and Ackroyd et al. [15] reported similar postoperative OKS results, which were 30.5 and 37 respectively. With respect to the KSS, our study found an increase from 56 preoperatively to 68.3 postoperatively. KSS functional score averaged 47.2 pre-operatively and 68.1 postoperatively. Mont et al. [25] reported that KSS final score improved from a mean of 64 before surgery to 87 after surgery, while functional scores improved from a mean of 48 to 82. Gao et al. [26] reported that KSS final score improved from 69.6 to 95.7 and functional scores improved from 53.6 to 95. These scores show that the outcomes of robotically assisted PFA are similar to other successful techniques. Dy et al. [7] reported that patients who undergo PFA rather than TKA are more likely to experience complications and require re-operation or revision, but subgroup analysis suggests a correlation with implant design. There was no significant difference in re-operation, revision, pain, or mechanical complications between second-generation PFA and TKA. Our
study had only one patient (3.2 %) who had required a reoperation to convert a PFA to a TKA. This was performed for persistent pain at another centre. Orthopedic surgery began to incorporate robotic technology in 1992 with the introduction of the ROBODOC, which assisted surgeons in the planning and performance of total hip replacement [27]. Advances in technology have allowed for the modern application of robotically assisted arthroplasty and it is making inroads into the practice of orthopedics. The most current devices were only made available a short time ago and as a result, studies inevitably involve short-term outcomes and limited patient numbers. Future studies will need to include longer follow-up and larger numbers of patients. The limitations of this paper are small numbers of patients and short-term follow-up.
Conclusions The early retrospective data for robotically assisted PFA show encouraging results. Advantages of this technique include a smaller incision, faster rehabilitation, preservation of bone stock, and implantation without malalignment [13, 28]. Preservation of bone stock is particularly beneficial if revision to a TKA is necessary. We believe that this technique will continue to demand attention and offer encouraging results in the future.
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Davies AP, Vince AS, Shepstone L, Donell ST, Glasgow MM (2002) The radiologic prevalence of patellofemoral osteoarthritis. Clin Orthop Relat Res 402:206–212 Ackroyd CE, Polyzoides AJ (1978) Patellectomy for osteoarthritis. A study of 81 patients followed for 2–22 years. J Bone Joint Surg 60-B:353–357 Laskin RS, Van Steijn M (1999) Total knee replacement for patients with patellofemoral arthritis. Clin Orthop Relat Res 367:147 Ackroyd CE, Chir B (2005) Development and early results of a new patellofemoral arthroplasty. Clin Orthop 436:7–13 Leadbetter WB, Ragland PS, Mont MA (2005) The appropriate use of patellofemoral arthroplasty: an analysis of reported indications, contraindications and failure. Clin Orthop 436:91–99 Cartier P, Sanouiller JL, Khefacha A (2005) Long-term results with the first patellofemoral prosthesis. Clin Orthop 436:47–54 Dy CJ, Franco N, Ma Y, Mazumdar M, McCarthy MM, Gonzalez Della Valle A (2011) Complications after patello-femoral versus total knee replacement in the treatment of isolated patello-femoral osteoarthritis. A meta-analysis. Knee Surg Sports Traumatol Arthrosc. doi:10.1007/s00167-011-1677-8 Heyse TJ, Khefacha A, Cartier P (2010) UKA in combination with PFR at average 12-year follow-up. Arch Orthop Trauma Surg 130(10):1227–1230 Confalonieri N, Manzotti A, Montironi F, Pullen C (2008) Tissue sparing surgery in knee reconstruction: unicompartmental (UKA),
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patellofemoral (PFA), UKA+PFA, bi-unicompartmental (Bi-UKA) arthroplasties. J Orthop Traumatol 9(3):171–177 Koller U, Apprich S, Domayer S, Windhager R, Trattnig S (2014) Magnetic resonance mapping of the rim of articular cartilage defects of the patella. Int Orthop 38(1):67–72 Petersen W, Rembitzki IV, Brüggemann GP, Ellermann A, Best R, Koppenburg AG, Liebau C (2014) Anterior knee pain after total knee arthroplasty: a narrative review. Int Orthop 38(2):319–328 Župan A, Snoj Ž, Antolič V, Pompe B (2014) Better results with patelloplasty compared to traditional total knee arthroplasty. Int Orthop 38(8):1621–1625 Zanasi S (2011) Innovations in total knee replacement: new trends in operative treatment and changes in peri-operative management. Eur Orthop Traumatol 2(1–2):21–31 Argenson JN, Flecher X, Parratte S et al (2005) Patellofemoral arthroplasty: an update. Clin Orthop Relat Res 440:50–53 Ackroyd CE, Newman JH, Evans R et al (2007) The Avon patellofemoral arthrolasty: five year survivorship and functional results. J Bone Joint Surg (Br) 89(3):310–315 Scheurer P, Reininga IH, van Jonbergen HP, van Raay JJ (2015) Secondary patellar resurfacing following total knee arthroplasty: a cohort study in fifty eight knees with a mean follow-up of thirty one months. Int Orthop. doi:10.1007/s00264-015-2684-z Schiavone Panni A, Cerciello S, Del Regno C, Felici A, Vasso M (2014) Patellar resurfacing complications in total knee arthroplasty. Int Orthop 38(2):313–317 Arciero RA, Toomey HE (1988) Patellofemoral arthroplasty. A three-to nine-year follow-up study. Clin Orthop Relat Res 236:60 Blazina ME, Fox JM, Del PW et al (1979) Patellofemoral replacement. Clin Orthop Relat Res 144:98–102
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de Winter WE, Feith R, van Loon CJ (2001) The Richards type II patellofemoral arthroplasty: 26 cases followed for 1–20 years. Acta Orthop Scand 72:487 21. van Jonbergen HP, Werkman DM, Barnaart LF, van Kampen A (2010) Long-term outcomes of patellofemoral arthroplasty. J Arthroplasty 25(7):1066–1071 22. Tauro B, Ackroyd CE, Newman JH, Shah NA (2001) The Lubinus patellofemoral arthroplasty. A five- to ten-year prospective study. J Bone Joint Surg (Br) 83:696–701 23. van Wagenberg JMF, Speigner B, Gosens T, Waal MJ (2009) Midterm clinical result of the Autocentric II patellofemoral prosthesis. Int Orthop 33:1603–1608 24. Odumenya M, Costa ML, Parsons N, Achten J, Dihillon M, Krikler SJ (2010) The Avon patellofemoral joint replacement five-years results from an independent center. J Bone Joint Surg (Br) 92-B: 56–60 25. Mont MA, Johnson AJ, Naziri Q, Kolisek FR, Leadbetter WB (2012) Patellofemoral arthroplasty: 7-year mean follow-up. J Arthroplasty 27(3):358-361 26. Gao X, Xu Z, He R, Yan S, Wu L (2010) A preliminary report of patellofemoral arthroplasty in isolated patellofemoral arthritis. Chin Med J 123(21):3020–3023 27. Lang JE, Mannava S, Floyd AJ, Goddard MS, Smith BP, Mofidi A, Seyler TM, Jinnah RH (2011) Robotic systems in orthopaedic surgery. J Bone Joint Surg (Br) 93(10): 1296–1299 28. Dabboussi N, Sakr M, Girard J, Fakih R (2012) Minimally invasive total knee arthroplasty: a comparative study to the standard approach. N Am J Med Sci 4(2):81–85
ORIGINAL PAPER
Short-term outcomes of robotically assisted patello-femoral arthroplasty Ugur Turktas 1 & Ahmet Piskin 2 & Gary G. Poehling 3
Received: 31 January 2015 / Accepted: 4 April 2015 # SICOT aisbl 2015
Abstract Purpose The purpose of this study was to determine the outcomes in patients treated with robotically assisted patellofemoral arthroplasty (PFA). Methods This technique offers a safe, reliable, and reproducible way of obtaining correct implant positioning in patello-femoral arthroplasty, and as a result, reduces revision surgery due to implant malalignment. We evaluated 30 knees in 29 patients who underwent robotically assisted patello-femoral arthroplasty between June 2009 and May 2011. Mean follow-up was 15.9 months. This was a retrospective study that involved chart reviews and radiographic analysis. Radiographic analysis included preoperative and postoperative plain films for implant positioning. Functional outcomes were evaluated using the Oxford Knee Score (OKS), range of motion, University of California at Los Angeles (UCLA) patient activity-level ratings, visual analog pain scale (VAS), and the Knee Society Score (KSS). Results The patients had an average OKS of 21.7 preoperatively and reached an average of 33.5 postoperatively (p = 0.0033). Pre-operative UCLA patient activity-level ratings was 3.1, compared with 4.8 postoperatively. Average VAS preoperatively was 8 and postoperatively it decreased to 2.1 (p = 0.0033). The average KSS final score pre-operatively
* Ugur Turktas [email protected] 1
Department of Orthopaedics and Traumatology, Turgut Ozal University School of Medicine, Ankara, Turkey
2
Department of Orthopaedics and Traumatology, Ondokuzmayis University School of Medicine, Samsun, Turkey
3
Department of Orthopaedic Surgery, Wake Forest University School of Medicine, Winston-Salem, NC, USA
was 56 and postoperatively it increased to 68.3 while the functional score pre-operatively was 47.2 compared to 68.1 postoperatively (p = 0.011). As a result, patello-femoral arthroplasty is an emerging knee resurfacing technique that is an alternative to the total knee arthroplasty. Conclusions The early retrospective data for roboticallyassisted PFA show encouraging results. Advantages of this technique include a smaller incision, faster rehabilitation, preservation of bone stock, and implantation without malalignment. Keywords Patello-femoral . Arthroplasty . Robotically controlled . Robot assisted . Osteoarthritis
Introduction Isolated patello-femoral osteoarthritis (PFOA) is a common disease. Approximately 10–15 % of patients who have knee pain manifest pathology consistent with PFOA. In a radiologic study of 206 knees in 174 consecutive orthopedic outpatients, Davies et al. [1] reported that the incidence of isolated PFOA is 13.6 % in women and 15.4 % in men older than age 60. The patients had anterior knee pain, particularly upon standing up from a chair or climbing stairs. There are multiple options for this disease if conservative treatment fails. These include arthroscopic debridement, patellectomy, chondroplasty, tibial tubercle transfer, total knee arthroplasty (TKA), and patellofemoral arthroplasty (PFA). Patellectomy was a more common treatment in the past, but long term results were poor [2]. Many orthopedic surgeons prefer TKA for advanced PFOA, and this treatment gives predictably good results [3]. However, PFA has become increasingly popular as it has the advantages of preserving the unaffected parts of knee, is less invasive than primary TKA, and may allow more rapid
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recovery [4]. Recent studies have shown better results with PFA as a result of improvements in the design and manufacturing of implants, better patient selection and an appreciation of the need to balance the soft tissue [5]. Cartier et al. [6] reported excellent functional outcomes in 77 % of patients at a mean follow-up of ten years. In these cases, patients should be selected carefully to ensure that there is not co-existent tibio-femoral arthritis. The most common cause of failure is progression of osteoarthritis in the tibio-femoral compartments [5, 7]. However, the association of a PFOA and unicompartmental (medial or lateral tibiofemoral compartment) knee osteoarthritis (UKOA) is commonly seen and is known as bi-unicompartmental osteoarthritis (biUKOA). In these patients, bi-unicompartmental knee a r t h r o p l a s t y ( P FA p l u s e i t h e r m e d i a l o r l a t e r a l unicompartmental arthroplasty, also referred to as bi-UKA) can be performed. Recent literature indicates satisfactory outcomes of this surgical procedure. Heyse et al. [8] reported high satisfaction at 12 years in patients that had bi-UKA, suggesting that this procedure can be successful in preventing TKA in mid- to long-term follow-up. Bi-UKA is particularly preferred in young and active patients who have PFOA and UKOA [9]. PFA utilizing conventional techniques has some complications, such as patellar catching, snapping, and implant malalignment. The purpose of our study is to report our short-term results of PFA using robotic arm assistance. Our hypothesis is that this robotic technique has the ability to produce a safe, reliable, and reproducible way of obtaining optimized component position and alignment, which will improve the clinical outcome as measured by the Oxford score.
Patients and methods Between June 2009 and May 2011, 30 consecutive PFAs with robotic arm assistance were performed in 29 patients with isolated PFOA or bi-UKOA. Of the 30 arthroplasties (14 right knee and 16 left knee), 13 patients received only a PFA, 17 patients had bi-UKA performed. Of the patients who had biUKA, all but one underwent the arthroplasty at the time of the index procedure. That individual had a medial UKA two years prior to an ipsilateral PFA. The average patient age was 66.4 years (range 37–83 years). There were ten men and 19 women. Average body mass index (BMI) was 32.4. In general, patients remained in the hospital only one night after surgery, except for one patient who had difficulty walking. The average length of hospital stay was 1.25 days. Indications for surgery including anterior knee pain when getting up from a seated position and going up or downstairs. Each operation was carried out by or under the direct supervision of the senior author (G.G.P.). All included patients suffered from PFOA or PFOA and medial or lateral tibiofemoral compartment osteoarthritis with obvious clinical and radiological findings. In bi-
UKAs, the tibiofemoral implants were placed laterally in four cases and medially in 13 cases. Patients were followed regularly with clinical and radiographic examinations. This retrospective study involved chart reviews and radiographic analysis. The patient information gathered from the chart review included age, gender, body mass index, diagnosis, length of hospital stay, co-morbidities and previous surgeries. Radiographic analysis was evaluated pre-operatively, postoperatively, and at every follow-up with weight-bearing anteroposterior, lateral, and sunrise views. We classified each patient pre-operatively using the Kellgren and Lawrance osteoarthritis scale on the anteroposterior views. Functional outcomes were evaluated using Oxford Knee Sore (OKS), range of motion (ROM), University of California at Los Angeles (UCLA) patient activity-level ratings, visual analog pain scale (VAS), and Knee Society Score (KSS). We used the modified method of calculating the OKS from 0 (worst outcome) to 48 (best outcome) to allow for comparison. Functional data were gathered at the pre-operative assessment and again at the six, 12-, and 24-month follow-ups. Only patients who had PFA with minimum six month follow-up were accepted into the study. Specifically, we evaluated the outcomes of PFA. The patients who were scheduled to have robotically assisted arthroplasty underwent multislice computerized tomography of the operative knee, and these images were used for pre-operative planning and registering. The computer within the robot used these data during surgery to display a three-dimensional reconstruction of the knee. We first registered the femur and then marked the level of the cartilage at the interface margins to help insure smooth transition. Then the position of the implant was manipulated on the computer to insure ideal conditions and smooth transitions. The surgeon performed the operation with assistance from the robot utilizing the three-dimensional reconstruction. Robotically-assisted PFA or bi-UKA requires about a 12-cm mid-patellar incision. The patellar articular surface was cut by an oscillating saw with a guide apparatus and while the trochlear area was carved by a high-speed burr on the robotic arm. The femoral condyle and tibial plateau were prepared in a similar fashion, utilizing the burr attached to the robotic arm to prepare the areas to accept the implants. With this particular system, the patellar and tibial inlay implants are both polyethylene, while the femoral implants are a chrome-cobalt material. Quicksetting methacrylate-based bone cement was used for cementation. Patients with obvious patellar maltracking underwent lateral release. The patients were allowed to fully weight-bear the follow day under the control of a physiotherapist. Generally, patients start physiotherapy two weeks after surgery and in progress for four to six weeks, two or three times a week. Average physiotherapy time was six weeks (two to 20 weeks).
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Statistical analysis For analysis we used the Wilcoxon (the non-parametric and two-sample test) test in SPSS 15 (SPSS, Chicago, IL).
Results We assessed 30 knees in 29 patients who had PFA or bi-UKA. Average follow-up was 15.9 months (seven to 30 months). All included patients suffered from PFOA or multicompartment osteoarthritis with obvious clinical and radiological findings. All patients had conservative treatment before the surgery, ten patients had a surgical procedure performed prior to PFA. Nine of these patients had arthroscopic knee surgery and one patient had it twice. Another patient had a medial compartmental UKA. One patient had a lateral tibial plateau fracture during the operation and received a lateral buttress plate for fixation. Thirty consecutive knees with patello-femoral arthritis patello-femoral arthroplasty proved to be ineffective treatment, three patients needed further arthroscopic debridement and only one patient had revision TKA after bicompartmental UKA for persistent pain and swelling, no patients had loosening of the implants. Two patients had arthrofibrosis, defined as having less than 90° of flexion, and one of them had manipulation under general anesthesia. Only one patient had an infection and it was treated with an open debridement, irrigation, and manipulation. One patient had persistent drainage and underwent arthroscopic debridement. One patient had a deep venous thrombosis 1 year after the surgery. One patient had a distal-third femoral stress fracture nine months after PFA, which went on to intramedullary nailing. The patients were evaluated with the Kellgren and Lawrance osteoarthritis scale. Patients had an average of 3.7 on the scale; only three joints had grade 2 osteoarthritis and eight joints had grade 3. Average ROM improved from 115° pre-operatively (90– 130°) to 123° postoperatively (110–130°), an overall average increase of 6.9 %. All patients who did not have a complication reached full ROM in 9.2 (two to 24) weeks on average. Only 30 % of all patients who had bi-UKA reached their full ROM before the 10th week, while 84.6 % of all patients who had PFA reached their full ROM before the tenth week. This result shows that rehabilitation after PFA is easier than bi-UKA rehabilitation and the patients who had PFA can reach a full ROM earlier than patients who had bi-UKA. There was not a distinct difference when BMI was taken into consideration. The patients had an average OKS of 21.7 (range 10–37) pre-operatively and reached an average of 33.5 (range 12–47) postoperatively (p = 0.0033) (Fig. 1). Pre-operative UCLA patient activity-level ratings was 3.1, compared with 4.8 postoperatively. Average VAS pre-operatively was 8 and postoperatively it decreased to 2.1 (p = 0.0033) (Fig. 2). The average
Fig. 1 OKS and KSS outcomes. Statistically significant improvements were observed in postoperative OKS and KSS outcomes (*p = 0.0033, **p = 0.011)
KSS final score pre-operatively was 56 (range 41–78) and postoperatively it increased to 68.3 (range 10–95), while the functional score pre-operatively was 47.2 (range 5–80) compared with 68.1 postoperatively (range 20–100) ( = 0.011). Robotically assisted patello-femoral arthroplasty demonstrated good or excellent results based on the OKS in 54.3 % at a minimum one year follow-up (Figs. 3, 4, 5 and 6).
Discussion We found that PFA was a very effective treatment for PFOA. The patients who had PFA or bi-UKA had very good results and this was particularly true for active patients. The goals of performing compartment-specific arthroplasty were to preserve the intact ligaments, maintain bone stock, and avoid replacing the unaffected compartments of knee. Similarly, we aimed to minimize our incision, allow easier rehabilitation, and return patients to their prior level of activity. Consequently, anterior knee pain, which is one of the most common causes of knee pain, is reduced [10–12]. Specifically, we used the robotically assisted PFA as a treatment for PFOA. Pre-operative planning with computed tomography and intraoperative registration allow for the correct positioning of the components. Even though TKA is commonly preferred in patients who have PFOA, we feel that robotically assisted, selective arthroplasty is not only less invasive, it also allows for faster rehabilitation then TKA [13]. Earlier PFA designs had less than optimal clinical results [5, 14], but more recent
Fig. 2 Pre-operative and postoperative VAS scores. Postoperatively the VAS scores were significantly decreased (*p = 0.0033). Before surgery the patients had significant knee pain; after surgery this pain primarily ended
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Fig. 5 Patello-femoral and medial tibiofemoral compartment OA view
Fig. 3 Knee sunrise, anteroposterior and lateral view, the lateral compartment is well preserved, however the patello-femoral and medial compartments demonstrate severe arthritis
same time, we performed robotically controlled arthroplasty to the other compartment of knee which had OA. We evaluated short-term outcomes of robotically controlled PFA or biUKA.
designs have been shown to be more successful [15]. At the
Fig. 4 Bi-UKA patello-femoral and medial femoral components. The articular defects of the trochlea and the medial femoral condyle are covered by the prosthesis. Note the smooth transition between the two components
Fig. 6 Operated knee anteroposterior-lateral-sunrise view, the medial compartment and patello-femoral compartment have been replaced and the lateral compartment has been preserved. The balance of the knee has been restored
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Scheurer et al. [16] reported that secondary patellar resurfacing led to patient satisfaction in 57 patients with persistent anterior knee pain following TKA. Seventy-four percent of patients were satisfied. Panni et al. [17] reported that when complications of the resurfaced patella occur, they can be potentially catastrophic events. PFA complications are different from secondary patellar resurfacing and re-operation after patellar resurfacing. Malalignment, related to the prosthesis design, was the most common reason for the failure of first-generation prostheses [7, 18–22]. Van Jonbergen et al. [21] reported that optimal positioning was determined by visual alignment of the long axis of the trial component with the trochlear groove. The same study reported that the revision rate for malposition was 7 %. Van Wagenberg et al. [23] reported that patient outcomes were far from satisfactory, even after revision to a TKA. Our work did not see any malalignment or maltracking. We feel that pre-operative planning with computed tomography and intraoperative registration help to prevent malalignment. Another common reason for revision is progression of tibio-femoral osteoarthritis [7, 21]. Our ability to evaluate this in our patient population was limited by our relatively shortterm analysis. Nevertheless, we did not observe any progression of tibio-femoral osteoarthritis. We evaluated the pre-operative and postoperative ROM. We observed that the patients average ROM increased from 115 to 123°. The patients who did not have a complication reached their full ROM in 9.2 weeks on average. Other recent studies reported similar results. Heyse et al. [8] reported that ROM improved from 107 to 121.1°, and Odumenya et al. [24] reported that the median range of movement pre-operatively was 120° and postoperatively was also 120°. The OKS and KSS for these patients were also very encouraging. On average, the postoperative OKS score was 33.5 compared with a pre-operative score of 21.7. Odumenya et al. [24] and Ackroyd et al. [15] reported similar postoperative OKS results, which were 30.5 and 37 respectively. With respect to the KSS, our study found an increase from 56 preoperatively to 68.3 postoperatively. KSS functional score averaged 47.2 pre-operatively and 68.1 postoperatively. Mont et al. [25] reported that KSS final score improved from a mean of 64 before surgery to 87 after surgery, while functional scores improved from a mean of 48 to 82. Gao et al. [26] reported that KSS final score improved from 69.6 to 95.7 and functional scores improved from 53.6 to 95. These scores show that the outcomes of robotically assisted PFA are similar to other successful techniques. Dy et al. [7] reported that patients who undergo PFA rather than TKA are more likely to experience complications and require re-operation or revision, but subgroup analysis suggests a correlation with implant design. There was no significant difference in re-operation, revision, pain, or mechanical complications between second-generation PFA and TKA. Our
study had only one patient (3.2 %) who had required a reoperation to convert a PFA to a TKA. This was performed for persistent pain at another centre. Orthopedic surgery began to incorporate robotic technology in 1992 with the introduction of the ROBODOC, which assisted surgeons in the planning and performance of total hip replacement [27]. Advances in technology have allowed for the modern application of robotically assisted arthroplasty and it is making inroads into the practice of orthopedics. The most current devices were only made available a short time ago and as a result, studies inevitably involve short-term outcomes and limited patient numbers. Future studies will need to include longer follow-up and larger numbers of patients. The limitations of this paper are small numbers of patients and short-term follow-up.
Conclusions The early retrospective data for robotically assisted PFA show encouraging results. Advantages of this technique include a smaller incision, faster rehabilitation, preservation of bone stock, and implantation without malalignment [13, 28]. Preservation of bone stock is particularly beneficial if revision to a TKA is necessary. We believe that this technique will continue to demand attention and offer encouraging results in the future.
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