SICOT e-Newsletter
Issue No. 59 - August 2013
Worldwide News
Inadequate 'three-point' proximal fixation predicts failure of the Gamma nailS. G. F. Abram, T. C. B. Pollard, A. J. M. D. Andrade
Royal Berkshire NHS Foundation Trust, Reading, United Kingdom
Bone Joint J 2013;95-B:825â30.
Comment by Shalin Maheshwari
| Abstract Introduction: Peritrochanteric fractures are commonly seen fractures in the elderly patients. Cephalomedullary nails provide a biomechanical advantage over sliding hip screws for unstable fracture patterns. The importance of the tipâapex distance (TAD) for fixation of the proximal fragment has been documented for both devices. For cephalomedullary nails, 'three-point' proximal fixation may confer additional stability and is one of the design features of the Gamma nail (Stryker, Newbury, United Kingdom). These three points are the cortical contact point of the lag screw at the lateral femoral cortex, the cortical contact point of the nail (or end-cap) at the greater trochanteric cortex, and the TAD of the lag screw. Whereas high TAD has been shown to predict failure rate in cephalomedullary nails, the importance of the other two points of proximal fixation has not yet been demonstrated. We hypothesized that mechanical failure of the Gamma nail was associated with inadequate proximal three-point fixation.
⨠Methods: A consecutive series of 299 Gamma 3 nails (Stryker) implanted in 299 patients over a five-year period between 1 January 2006 and 31 December 2010. A total of 76 patients were excluded leaving a total of 223 patients for inclusion in the study. Post-operatively, all patients were allowed to partially bear weight, building to full weight-bearing over a period of six weeks.⨠Results: A total of 16 failures were identified at a mean time post-operatively of 15.6 weeks (2 to 70): 12 due to fixation failure, three to nail fractures and one due to nail subsidence. Summary: Mechanical failure of the Gamma nail in peritrochanteric femoral fractures is rare (< 1%) when three-point proximal fixation is achieved. However, when proximal fixation is inadequate, failure rates increase. The strongest predictor of failure is positioning the lateral end of the lag screw short of the lateral cortex. Adherence to simple technical points minimizes the risk of fixation failure in this vulnerable patient group. |
Comment
Peritrochanteric fractures have always fascinated orthopaedic surgeons with regards to choice of implant. They can be difficult to treat but the treatment options and indications are fairly well described in most cases. In a recent Cochrane review, Parker et al (2010) showed higher complication rate associated with cephalomedullary devices and recommended further studies using more contemporary implants. Most biomechanical evaluations of the Gamma nail have focused on the inherent differences between it and a sliding hip screw, particularly with respect to the lever arm on the fracture, cut-out from the head, stress-shielding at the calcar, and dynamic sliding of the lag screw. Abram et al have shown us three precise radiological criteria to aim for when using a cephalomedullary nail to fix a fracture of the proximal femur. Their statistical analysis highlighted that both a tip-apex distance of more than 25mm and the absence of penetration of the lag screw through the lateral cortex were associated with failure. When all three radiological criteria were present, the failure rate was less than 1% and when all three were absent it was 7.2%.
The strengths of this study include the large sample size studied over a five-year period, the reliability of the measurements made and the multivariate analysis, which adjusted for important confounding variables. However, there were few limitations, the authors were unable to accurately account for the grade of operating surgeon, mechanism of injury and not follow up all patients up to radiological union. Also the third criterion of protrusion of the proximal end of the nail through the tip of the greater trochanter did not predict failure significantly. I quote comments of Cyril Mauffrey and Philip Stahel in agreement of our and their experience that radiological finding of a high-riding lag screw can be improved by over-sinking the nail, as there is a natural tendency for the nail to migrate proximally while it is being manipulated to allow insertion of the lag screw. Breaching of the lateral cortex by the distal end of the lag screw should be kept to a minimum to prevent irritation of the ilio-tibial band. Meticulous planning and attention to detail will determine the success or failure of this implant and reflects the operator dependency of this type of surgery. The extra ten minutes needed to perfect the position, accuracy of reduction and length of the lag screw will prove to be beneficial for patients, with a lower rate of failure and revision.
This paper by Abram et al has the potential to change medical practice by drawing the attention of the surgical team to new radiological criteria. Overall it is a good study and I would like to implement three-point proximal fixation in peritrochanteric fractures in my routine practice. However, these results should be corroborated by further larger, multicentric, randomized controlled trials to recommend it strongly as a protocol in radiological assessment of these fractures under treatment and serve as a prognostic value for failure in treatment with gamma nail.
The strengths of this study include the large sample size studied over a five-year period, the reliability of the measurements made and the multivariate analysis, which adjusted for important confounding variables. However, there were few limitations, the authors were unable to accurately account for the grade of operating surgeon, mechanism of injury and not follow up all patients up to radiological union. Also the third criterion of protrusion of the proximal end of the nail through the tip of the greater trochanter did not predict failure significantly. I quote comments of Cyril Mauffrey and Philip Stahel in agreement of our and their experience that radiological finding of a high-riding lag screw can be improved by over-sinking the nail, as there is a natural tendency for the nail to migrate proximally while it is being manipulated to allow insertion of the lag screw. Breaching of the lateral cortex by the distal end of the lag screw should be kept to a minimum to prevent irritation of the ilio-tibial band. Meticulous planning and attention to detail will determine the success or failure of this implant and reflects the operator dependency of this type of surgery. The extra ten minutes needed to perfect the position, accuracy of reduction and length of the lag screw will prove to be beneficial for patients, with a lower rate of failure and revision.
This paper by Abram et al has the potential to change medical practice by drawing the attention of the surgical team to new radiological criteria. Overall it is a good study and I would like to implement three-point proximal fixation in peritrochanteric fractures in my routine practice. However, these results should be corroborated by further larger, multicentric, randomized controlled trials to recommend it strongly as a protocol in radiological assessment of these fractures under treatment and serve as a prognostic value for failure in treatment with gamma nail.