Technology and Health Care 22 (2014) 909–913 DOI 10.3233/THC-140864 IOS Press

909

Minimally invasive stabilization of distal humerus fractures: A pilot study with biomechanical evaluation K. Reising∗ , L. Konstantinidis, P. Helwig, F.C.L. Wagner, N.P. Südkamp and P.C. Strohm Department of Surgery, Clinic for Orthopedic and Trauma Surgery, Freiburg University Hospital, Freiberg, Germany Received 2 July 2014 Accepted 15 September 2014 Abstract. BACKGROUND: Fracture of the distal humerus is a fairly rare injury and makes high demands on the treating surgeon. Prerequisites for a good outcome are anatomical reconstruction and osteosynthesis stable enough for exercises. A method permitting early restoration of function is especially important for patients with osteoporosis. The extensive surgical approach necessary for open reduction is associated with a high number of wound healing disorders and infections with a frequency of 11% being reported in the literature. Although open reduction and internal fixation in double-plating technique is unavoidable for complex intraarticular fractures, an alternative, minimally invasive and, consequently, tissue-preserving procedure is desirable for simpler fractures. OBJECTVE: To investigate this issue further an angular stable nail system developed for the distal radius was implanted as a stabilizer and the construct tested biomechanically as part of a feasibility study. METHODS: Distal humerus fractures were stabilized by insertion of a distal radius nail, namely, the Targon DR (Aesculap, Tuttlingen) and a K-wire. To test the hypothesis six cadaveric bones fixed in formalin were tested biomechanically for displacement, implant failure, and stiffness. Displacement was determined by means of an ultrasound-based system. RESULTS: An average displacement of 1.6 mm ± 0.7 was recorded at a maximum compression force of 100 N in extension and an average displacement of 1.4 mm ± 0.9 in flexion. Implant failure was not observed for any of the constructs. CONCLUSIONS: The study presented here permits the conclusion that a minimally invasive procedure is possible at the distal humerus and does ensure adequate stability. Although the nail was not specifically designed for the humerus, current findings form the basis for a promising approach that will be pursued further after modification of the nail design. Keywords: Distal humerus fracture, minimal invasive, nail osteosynthesis, angular stable

1. Introduction Distal humerus fracture is a rather rare injury, accounting for 2–6% [1–3] of all fractures and makes high demands on the treating surgeon. It frequently occurs in an environment of osteoporotic bone and the highest incidence is seen in older women [1–4]. Since a longer period of immobilization is accompanied by arthrofibrosis and poor functional outcomes [5,6], anatomical reconstruction and osteosynthesis ∗ Corresponding author: Kilian Reising, Department of Surgery, Clinic for Orthopedic and Trauma Surgery, Freiburg University Hospital, Hugstetter Str. 55, D- 79106 Freiburg, Germany. E-mail: [email protected].

c 2014 – IOS Press and the authors. All rights reserved 0928-7329/14/$27.50 

910

K. Reising et al. / Minimally invasive stabilization of distal humerus fractures

Fig. 1. X-ray after osteosynthesis.

Fig. 2. Experimental setup a: medial view b: lateral view. (Colours are visible in the online version of the article; http://dx.doi. org/10.3233/THC-140864)

stable enough for exercises are preconditions for a good outcome with a satisfactory range of motion and few symptoms. The extensive approach necessary for open reduction is associated with a high risk of wound healing disorders and infections, which is quoted in the literature at 11% [4,7], and occurs preferentially in older patients with a poorer soft tissue situation. Although open reduction and internal fixation by double-plating is imperative in the treatment of complex intraarticular fractures, the question of an alternative, minimally invasive, soft-tissue preserving procedure arises with regard to simpler fractures. To address this question a nail system originally designed for the distal radius was tested as an alternative stabilizer. 2. Methods A distal radius nail (Targon DR, Aesculap, Tuttlingen) and a K-wire (1.8 mm) were inserted to stabilize distal humerus fractures. Biomechanical testing was conducted on six cadaveric bones fixed in formalin. First, a standardized osteotomy was created in all humeri to simulate a distal humerus fracture (type 13A2). Next, osteosynthesis was performed by inserting the Targon DR nail through the radial column. First, the cortical bone in the region of the radial epicondyle was opened and after reaming, the nail was inserted. Next, two proximal 2.3 mm screws and four distal locking 2.2 mm screws were introduce

K. Reising et al. / Minimally invasive stabilization of distal humerus fractures

911

Table 1 Results dislocation (mm) Extension load Mean Median (min; max) n Flexion load Mean Median (min; max) n

1.6 ± 0.7 1.5 0.9; 2.3 6 1.4 ± 0.9 1.0 0.5; 2.5 6

through the aiming device. To ensure rotational stability the ulnar column was also stabilized by placement of a 1.8 mm K-wire inserted via the medial epicondyle. All fixations were performed by the same traumatologist. Correct implant placement was assessed radiologically (Fig. 1). After osteosynthesis the humeri were shortened to a length of 14 cm and embedded to a length of 5 cm in the steel cylinders of the Universal Testing System (UTS 20/Zwick testControl, Zwick, Ulm, Germany). Loading consisted of compression loading from posterior to anterior to simulate extension and flexion load. In accordance with the test protocol cyclic, force-controlled displacement at alternating loads of between 5 N and 100 N at a speed of 50 N/sec were performed (Fig. 2). Fragment displacement was recorded with an ultrasound based three-dimensional motion analysis system with an accuracy of 0.1 mm (CMS 20, Zebris Medical, Isny, Germany). The sensors were attached to the distal humerus by insertion of 4.0 mm pins. Microsoft Excel was utilized for data analysis. All humeri were human cadaver humeri provided by the anatomical institute of the University of Freiburg. Every donator signed in the lifetime an agreement form for using his remains for teaching and science.

3. Results At a maximum pressure of 100 N in extension load there was an average displacement of 1.6 ± 0.7 mm (med 1.5 mm/min; max 0.9; 2.3 mm). In flexion an average displacement of 1.4 ± 0.9 mm (med 1.0 mm/ min; max 0.5; 2.5 mm) was recorded. Implant failure was not observed for any of the constructs. Testing to determine construct strength in flexion yielded an average of 49.0 ± 12.9 N/mm (med 48.7 N/mm; min; max 26.6; 82.9 N/mm), and in extension 55.9 ± 10.5 N/mm (med 56.9 N/mm; min; max 34.7; 71.0 N/mm). Implant failure was not observed in any case. Radiological assessment of all constructs revealed intact standardized osteosyntheses.

4. Discussion Distal humerus fractures are a challenge even to the experienced surgeon due to the complexity of the fractures and the often difficult soft tissue situation [8]. Numerous different fixation procedures have been investigated in the past [6,9]. However, a multiplicity of complications have been observed in older patients [4,8,10].

912

K. Reising et al. / Minimally invasive stabilization of distal humerus fractures

The key problem of implant failure with rates of up to 30% [11,12] has been importantly reduced by the introduction of locking implants [13]. The implant under investigation also utilizes this advantage since rotational stability is achieved by insertion of appropriate screws in combination with intramedullary implantation. Implant failure was not observed for any construct in the biomechanical study reported here. The construct stiffness data obtained is highly comparable to the results of other study groups. Caravaggi et al. [14] found, as have earlier groups [3], higher stiffness values for plates positioned in parallel. Our results correspond to the values they recorded for plates positioned at right angles, i.e. a stiffness of 50 N/mm. Complications associated with the approach also play an important role in daily clinical routine. The infection rate of up to 11% [15,16] is well above the rates for other osteosyntheses. This is certainly due in part to limited soft tissue coverage combined with a lengthy operation time. To avoid further compromise of the soft tissues, Walz et al achieved good results in their case series with an osteosynthesis consisting of isolated percutaneous screws combined with a fixator [17]. However, this procedure required immobilization for six weeks. Screw fixation alone performed in open surgical technique was described by Zagorski et al. [18] and good to very good outcomes were achieved, whereby the patients were younger with an average age of 45 years. In contrast, Papaioannou et al found far better outcomes in their patient sample for their custom-made, minimal plate osteosynthesis (Steinmann pins and screws) with additional immobilization in plaster [19]. In the technique reported here osteosynthesis is performed through a 3 cm long approach, whereby the implant is completely countersunk below the level of the bone so that it cannot cause any soft tissue irritation. Another complication with a reported incidence of 15% can be prevented by minimally invasive technique, namely, injury to the ulnar nerve [20]. In our technique there is no need to expose the nerve, thus avoiding any potential impairment. The implant tested in the present study is a rotationally stable, locking nail, stable enough to permit functional rehabilitation in daily routine and is combined with a tissue-friendly surgical technique. No similar implant was tested before for treatment of distal humerus fractures. One limitation of the study is definitely the focus on an ‘A’ fracture pattern that is rarely seen in clinical routine. Modification of the implant, particularly, by lengthening the intramedullary anchorage, would however certainly permit stabilization of B and C1 injuries. The current investigation was conducted as a pilot study that did not include a control group. Comparison of stiffness data with other research findings showed that our method is promising but it does require renewed testing with a control group after appropriate modification of the implant. The study was performed on cadaveric bones fixed in formalin. These were well suited to a pilot study, however, more extensive investigation should be carried out on fresh frozen bones to ensure comparable biomechanical properties to living bone [21]. 5. Conclusion The study presented here permits the conclusion that a minimally invasive and procedure is possible at the distal humerus and can guarantee sufficient stability. Although the implant was not specifically designed for the humerus, the technique under investigation appears promising. Future studies are needed to further evaluate the method by modification of nail design and direct comparison with existing procedures. All authors have disclosed any financial and personal relationships with other people or organizations that could have inappropriately biased this work.

K. Reising et al. / Minimally invasive stabilization of distal humerus fractures

913

References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21]

Rueger JM, Janssen A, Barvencik F, Briem D. [Bicondylar fracture of the distal humerus]. Unfallchirurg. 2005; 108: 59-61. Rueger JM, Rucker A, Briem D. [Distal fracture of the humerus]. Chirurg. 2007; 78: 959-71; quiz 72. Stoffel K, Cunneen S, Morgan R, Nicholls R, Stachowiak G. Comparative stability of perpendicular versus parallel double-locking plating systems in osteoporotic comminuted distal humerus fractures. J Orthop Res. 2008; 26: 778-84. Srinivasan K, Agarwal M, Matthews SJ, Giannoudis PV. Fractures of the distal humerus in the elderly: Is internal fixation the treatment of choice? Clin Orthop Relat Res. 2005: 222-30. John H, Rosso R, Neff U, Bodoky A, Regazzoni P, Harder F. Operative treatment of distal humeral fractures in the elderly. J Bone Joint Surg Br. 1994; 76: 793-6. Jupiter JB, Neff U, Holzach P, Allgower M. Intercondylar fractures of the humerus. An operative approach. J Bone Joint Surg Am. 1985; 67: 226-39. Korner J, Diederichs G, Arzdorf M, Lill H, Josten C, Schneider E, et al. A biomechanical evaluation of methods of distal humerus fracture fixation using locking compression plates versus conventional reconstruction plates. J Orthop Trauma. 2004; 18: 286-93. Huang TL, Chiu FY, Chuang TY, Chen TH. The results of open reduction and internal fixation in elderly patients with severe fractures of the distal humerus: A critical analysis of the results. J Trauma. 2005; 58: 62-9. Doornberg JN, van Duijn PJ, Linzel D, Ring DC, Zurakowski D, Marti RK, et al. Surgical treatment of intra-articular fractures of the distal part of the humerus. Functional outcome after twelve to thirty years. J Bone Joint Surg Am. 2007; 89: 1524-32. John SD, Wherry K, Swischuk LE, Phillips WA. Improving detection of pediatric elbow fractures by understanding their mechanics. Radiographics. 1996; 16: 1443-60; quiz 63-4. Korner J, Lill H, Muller LP, Hessmann M, Kopf K, Goldhahn J, et al. Distal humerus fractures in elderly patients: results after open reduction and internal fixation. Osteoporos Int. 2005; 16 Suppl 2: S73-9. Sodergard J, Sandelin J, Bostman O. Mechanical failures of internal fixation in T and Y fractures of the distal humerus. J Trauma. 1992; 33: 687-90. Reising K, Hauschild O, Strohm PC, Suedkamp NP. Stabilisation of articular fractures of the distal humerus: Early experience with a novel perpendicular plate system. Injury. 2009; 40: 611-7. Caravaggi P, Laratta JL, Yoon RS, Biasio JD, Ingargiola M, Frank MA, et al. Internal Fixation of the Distal Humerus: A Comprehensive Biomechanical Study Evaluating Current Fixation Techniques. J Orthop Trauma, 2013. Srinivasan K, Agarwal M, Matthews SJ, Giannoudis PV. Fractures of the distal humerus in the elderly: Is internal fixation the treatment of choice? Clin Orthop Relat Res. 2005: 222-30. Korner J, Lill H, Muller LP, Hessmann M, Kopf K, Goldhahn J, et al. Distal humerus fractures in elderly patients: Results after open reduction and internal fixation. Osteoporos Int. 2005; 16 Suppl 2: S73-9. Walz M, Auerbach F. [Distal intraarticular humerus fractures in elderly patients. Treatment with combined percutaneous screw fixation and an external fixator]. Unfallchirurg. 2006; 109: 940-7. Zagorski JB, Jennings JJ, Burkhalter WE, Uribe JW. Comminuted intraarticular fractures of the distal humeral condyles. Surgical vs. nonsurgical treatment. Clin Orthop Relat Res. 1986: 197-204. Papaioannou N, Babis GC, Kalavritinos J, Pantazopoulos T. Operative treatment of type C intra-articular fractures of the distal humerus: The role of stability achieved at surgery on final outcome. Injury. 1995; 26: 169-73. Jupiter JB, Neff U, Holzach P, Allgower M. Intercondylar fractures of the humerus. An operative approach. J Bone Joint Surg Am. 1985; 67: 226-39. Unger S, Blauth M, Schmoelz W. Effects of three different preservation methods on the mechanical properties of human and bovine cortical bone. Bone. 2010; 47: 1048-53.

Copyright of Technology & Health Care is the property of IOS Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.

Minimally invasive stabilization of distal humerus fractures: a pilot study with biomechanical evaluation.

Fracture of the distal humerus is a fairly rare injury and makes high demands on the treating surgeon. Prerequisites for a good outcome are anatomical...
659KB Sizes 3 Downloads 10 Views