The first choice for management of a periprosthetic fracture is long stem revision arthroplasty, however, many elderly patients are unable to undergo the lengthy surgical procedure necessary. Open reduction and internal fixation may be used as an alternative method of treatment provided the prosthesis stem is stable. Internal fixation methods include cerclage wires with or without cortical strut allografts; dynamic compression plate with screws; Dall-Miles (or similar) plate with cables and screws (unicortical and bicortical) and the Mennen Femur Plate.

Figure 1: Mennen Femur Plate

The internal fixation devices used in the treatment of femoral periprosthetic fractures usually rely on ‘rigid’ fixation involving considerable soft tissue dissection, which adversely affects the biological mechanisms for bone healing. The Mennen Plate is designed to provide sufficient stabilisation without stress shielding to facilitate fracture healing whilst permitting physiological micro-movement at the fracture site. The plate has minimum contact with bone thus preserving the periosteum, promoting callus formation and helping the bone regain its normal architecture more quickly. The surgical procedure is short, making the plate a useful treatment in the frail elderly patient.

Figure 2: Clinical use of the Mennen Femur Plate for the treatment of a femoral periprosthetic fracture (reprinted with permission from CH Medical Ltd.).

The Mennen Femur Plate has been used successfully in the management of periprosthetic fractures, in many countries, as evidenced by a number of published clinical results.^1,2 However, less favourable results have also been reported.^3,4 A detailed review of the literature revealed a clinical success rate of more than 85% which compares well to other treatments.

It should also be borne in mind that due to its atraumatic technique the Mennen Plate is often used in the most challenging cases – severe osteoporosis, poor general health, impaired mental status. It is estimated from clinical results that the failure incidence due to plate fracture is 7.1%, due to plate bending is 1.3% and failure of the operative technique resulting in non-union occurs in 6% of all the reported cases. The possible causes of failure include static overload, metal fatigue, material defects, surgical technique, instrumentation and deviation from the recommended post-operative regime.

The geometry of the new plate has been optimised using advanced engineering techniques including Computer Aided Design (CAD) and Finite Element Modelling (FEM). Manufactured from advanced stainless steel alloy, the 3rd Generation Plate has significantly improved mechanical properties including fatigue life. Enhanced stability at the fracture site results from the optimised mechanical strength, which has been increased by a factor of almost 2.5.

Figure 3: Von Mises stress field in the middle area of the upper surface for the 3rd generation (shown left) and current (shown right) plates under same loading

Figure 4: Comparison of flexural strength

Figure 5: Comparison of flexural rigidity

Laboratory evaluation, including analysis of the load deformation response and stress/strain distribution, showed that the new plate consistently produced lower deformation with a better and more uniform stress/strain pattern (Figure 3) for a given applied bending moment. The new plate has greatly increased flexural strength (Figure 4) and flexural rigidity (Figure 5)

The minimum contact design of the new plate ensures contact with only 15% of the bone surface thus preserving the periosteum and conserving the blood supply at the fracture site, permitting biological healing⁶ and avoiding bone necrosis under the plate. The minimum contact design also addresses the problem presented with the osteoporotic patient. In unstable fractures enhanced fixation security is achieved with the stabiliser fins and augmented fixation.

1. Kligman, M., Otramsky, I., Roffman, M.: Conservative versus surgical treatment for femoral fracture after total or hemiarthroplasty of hip, Arch. Orthop. Trauma Surg., 1999, 119, 79-81
2. Uchio, Y., Shu, N., Nishikawa, U., Takata, K., Ochi, M.,: Mennen plate fixation for fractures of the femoral shaft after ipsilateral hip arthroplasty, J. Trauma, 1997, 42(6), 1157-1160
3. Noorda, J.P., Wuisman, P.I.J.M.: Mennen Plate Fixation for the Treatment of Periprosthetic Femoral Fractures, J. Bone Joint Surg. [Am], 2002, 84(12), 2211- 2215
4. Kamineni, S., Ware, H.E.: The Mennen plate: unsuitable for elderly femoral periprosthetic fractures, Injury, 1999, 30, 257-260
5. Pappas, C.A., Young, P.G., Lee, A.J.C.: “Redesign of a Periprosthetic Fracture Plate using Finite Element Analysis”. International Congress on Computational Bioengineering, 13A, Zaragosa, Espana, Vol. 1, 2003, 61-64
6. Perren, S.M.: Background of the technology of internal fixators Injury, 2003, 34 S-B1-S-B3

Mr D McMinn

Mr J Cobb

Mr D Fern

Mr M Porter

Miss S Muirhead-Allwood

Prof D Murray

On 11th to 14th of November 2004 in Dubai, 260 surgeons from 27 countries gathered at the Madinat Jumeirah Convention Centre to participate in Smith & Nephew’s Second International Hip Resurfacing Forum. Professor David Murray from Oxford, UK and Dr David Young from Melbourne, Australia, chaired the meeting jointly. Over two days, the prestigious international faculty gave presentations and lead debate on one of the hottest topics in current Orthopaedics in conjunction with other related issues.

The first session of the programme – ‘Wear of Metal/Metal Bearings – Issues’ was chaired by Dr Len Walter (Australia) and set out to bring to the fore the current issues relating to Friction, Wear and Lubrication.

This session included the evaluation of retrieved components, which confirmed the comparable performance of the Birmingham Hip Resurfacing (BHR) material triboligical properties with those of the successful long-term first generation devices on which its specification was based.

The second session of the programme – ‘Resurfacing in Action’ saw presentations from Belgium, Australia, Ireland and the UK showing the results of their resurfacings with the Birmingham Hip Resurfacing device and clearly setting out the advantages and issues associated with the use of resurfacing. To date their have been over 40,000 BHR’s implanted worldwide.

In the next two sessions, presenters discussed criteria under the ‘Clinical Consideration’ subject matter; ‘Patient Selection’, ‘RSA Study of the BHR’, ‘Bone conservation in resurfacing’, ‘Ganz approach for the Resurfacing’ and issues associated with complex hip resurfacing. Alternate Bearing options, such as Oxinium was also presented.

The second day of the forum commenced with session five in which presenters from the UK and Australia discussed issues such as; ‘Complications of the BHR’. In this session the international faculty addressed the issues concerning the management of femoral neck fracture and related topics such as ‘Femoral head vascularity after Resurfacing’

The following session opened with a look at current clinical issues regarding Minimal Invasive Surgery and Navigation. Surgeons from the UK, Germany, Switzerland and Australia discussed their global experiences in this evolving surgical sub speciality. The session concluded with a presentation from Mr Derek McMinn (above right), UK, the pioneer of the modern day metal-on-metal resurfacing, who has been developing the MIS approach for the BHR.

The final session saw presenters debate the topic of ‘Avascular Necrosis of the Femoral Head’. Shared experiences from India, Korea, Sweden and the UK demonstrated the successful use of the BHR for this clinical indication.

Dr David Young from Melbourne closed this part of the forum and thanked Smith & Nephew for their support in convening an interesting and stimulating meeting.

Later that same afternoon, a different scene was set for the ‘Masterclass’ which invoked the shared experiences of surgical expertise concerning the resurfacing technique. Mr Martyn Porter (Wrightington, UK) moderated this session (below) and stimulated an international panel of experts to discuss the various surgical nuances concerning resurfacing arthroplasty including surgical technique, approaches and soft tissue dissection.

The second session saw discussion and debate concerning ‘Pushing the boundaries’. Surgical issues such as Dysplasia, Osteotomy and SUFE were presented and lively dialogue among the panel and delegates brought this interesting session to a close.

The 2nd International Resurfacing Forum was officially concluded when delegates and partners convened at the acclaimed seven star ‘Burj Al Arab’ hotel for pre-dinner drinks followed by evening dinner within the grounds of the Jumeirah Beach Hotel complex.

An address from Mr Dave Illingworth, president of Smith & Nephew Orthopaedics, thanked the delegation for making the forum an interesting and successful meeting.

Figure 1: An Orthogonal View of the X STOP Implant The tissue expander allows for ease of insertion in the interspinous space and the spacer resists extension of the stenotic level. The wings prevent lateral and anterior migration, and the supraspinous ligament prevents posterior migration. The X STOP is placed between the spinous processes of the affected level.

Based on the dynamic nature of the condition, a novel interspinous implant (The X STOP® Interspinous Process Distraction (IPD) System (“X STOP”), St Francis Medical Technologies, Concord, CA, USA, see Figure 1) was developed to be implanted using a minimally invasive procedure under local anaesthesia.

Figure 2: The implant is placed between the spinous processes of the affected level(s) and prevents extension at those levels.

The X STOP design was based on clinical findings that patients obtain pain relief from neurogenic claudication symptoms during sitting and flexion and have onset of symptoms during standing, walking and extension. The implant is placed between the spinous processes of the affected level(s) and prevents extension at those levels (see Figure 2). Following this design concept, a series of biomechanical studies were performed to test the biomechanical safety and efficacy on such a novel implant.

A study using magnetic resonance imaging (MRI) images to measure spinal canal and foraminal dimensions determined that, during extension, the levels implanted with the X STOP had an increase in canal area, canal diameter and subarticular diameter of 18%, 10% and 50%, respectively; the foraminal area and width increased by 25% and 41%, respectively.² Kinematics studies demonstrated that the X STOP decreases the range of motion in extension, but does not affect axial rotation or lateral bending.³

Also, the kinematics of the adjacent levels are unaffected. Finally, two studies that focused on disc pressure and facet pressure concluded that the disc pressure decreased by 63% in the posterior annulus and 41% in the nucleus during extension,⁴ and the mean facet pressure decreased by 58%.⁵ The disc pressure and facet load were unaffected at the adjacent levels. The biomechanical findings demonstrate that the X STOP:

• will not result in spinous process fractures;
• will not dislodge or migrate from the interspinous space;
• is effective in preventing narrowing of the spinal canal and neural foramina;
• allows unrestricted axial rotation and lateral bending;
• reduces disc pressure and facet loads; and
• does not affect the adjacent levels.

Patients were followed for two years after treatment and, at each follow-up visit of six weeks, six months, one year and two years, patients completed a Zurich Claudication Questionnaire (ZCQ) that assessed the patients’ symptoms and function specific to INC.^9,10 The ZCQ is a validated outcomes measure that quantifies a patient’s clinical success in symptom severity, physical function and satisfaction.

The mean age of the patients in both groups was approximately 70 years. The mean operative time for the X STOP procedure was 51 minutes for a single level and 59 minutes for a double level and there was less than 60cc of blood loss in either case. All cases but three were performed under local anaesthesia and 95% of the patients returned home in less than 24 hours.

At 24 months, 65% of the patients had clinical improvement in symptom severity, 64% had clinical improvement in physical function and 77% were satisfied. On the other hand, in the control group, 34% had clinical improvement in symptom severity, 30% had clinical improvement in physical function and 53% were satisfied.

During the study, nine X STOP patients and 26 control patients elected to undergo a laminectomy procedure due to lack of pain relief and completed a ZCQ following their laminectomy. Following the laminectomy, 63% of the patients had clinical improvement in symptom severity, 69% had clinical improvement in physical function and 63% were satisfied.

In addition to the results presented in the current study, Katz, et al. reported on 199 INC patients treated with a lumbar laminectomy.11 The patients were assessed using the same ZCQ presented in the current study; however, not all of the same results were reported by Katz, et al.

Unpublished data of this patient population, however, demonstrates that 63% of the patients had clinical improvement in symptom severity, 59% had clinical improvement in physical function and 72% were satisfied. These values are similar to those of the X STOP patients and laminectomy patients in the current study (see Figure 3) and suggest that the X STOP IPD system is as effective as a laminectomy.

Figure 3: ZCQ Success Rates for the X STOP, Control, Laminectomy Patients in the Current Study and Laminectomy Patients Reported by Katz, et al.

In addition, there were no major intraoperative or post-operative complications that occurred as a result of the procedure. The complications that occurred included a posteriorly dislodged implant in one patient following a traumatic fall, an asymptomatic spinous process fracture occurred between the six-week and six-month visits, one haematoma and one wound dehisence.

The dislodged implant was removed without sequale and the spinous process fracture healed without affecting the patient’s clinical success. These complications are relatively minor compared with those associated with a laminectomy such as dural tears, neural injury, deep wound infection, pulmonary embolism, myocardial infarction and death. This suggests that the X STOP procedure is a much safer treatment for INC than a laminectomy that requires general anaesthesia and is performed directly adjacent to the neural structures.

In the continuum of the treatment options for patients with INC, the X STOP offers the immediate and long-lasting effectiveness of a laminectomy with the safety of conservative care.

In summary, the X STOP IPD procedure:

• can be performed under local anaesthesia on an out-patient basis;
• does not require removal of bone or soft tissue;
• is safe and effective;
• is less costly than a laminectomy; and
• is clinically proven.

1. S Yerby, D Lindsey and J Kreshak, “Failure load of the lumbar spinous process”, International Society for the Study of the Lumbar Spine (2001), Edinburgh.
2. J Richards, S Majumdar and D Lindsey, et al., “Quantitative changes in the lumbar spinal canal with an interspinous implant”, International Meeting on Advanced Spine Techniques (2002), Montreux, Switzerland.
3. S Yerby, D Lindsey and K Swanson, et al., “Influence of an interspinous spacer on the kinematics of the lumbar spine”, Eurospine (2002), Nantes, France.
4. K E Swanson, D P Lindsey and K Y Hsu, et al., “The effects of an interspinous implant on intervertebral disc pressures”, Spine, 28(1) (2003), pp. 26–32.
5. C Wiseman, D Lindsey and S Yerby, “The effect of an interspinous spacer on facet load during extension”, International Society for the Study of the Lumbar Spine (2003), Vancouver, Canada.
6. K Hsu, J Zucherman and C Hartjen, et al., “Symptom severity outcomes in lumbar stenosis patients treated with the X STOP interspinous process spacer and non-operative treatment”, Spine Across the Sea (2003), Maui, Hawaii.
7. K Hsu, J Zucherman and C Hartjen, et al., “The X STOP interspinous implant improves physical function in lumbar spinal stenosis patients”, International Society for the Study of the Lumbar Spine (2003), Vancouver, Canada.
8. J Zucherman, K Hsu and C Hartjen, et al., “Multicenter randomized prospective trial for treatment of lumbar neurogenic claudication with an interspinous device: one-year results”, International Society for the Study of the Lumbar Spine (2002), Cleveland, OH.
9. G Stucki, L Daltroy and M H Liang, et al., “Measurement properties of a self-administered outcome measure in lumbar spinal stenosis”, Spine, 21(7) (1996), pp. 796–803.
10. G Stucki, M H Liang and A H Fossel, et al., “Relative responsiveness of condition-specific and generic health status measures in degenerative lumbar spinal stenosis”, J. Clin. Epidemiol., 48(11) (1995), pp. 1,369–78.
11. J N Katz, G Stucki and S J Lipson, et al., “Predictors of surgical outcome in degenerative lumbar spinal stenosis”, Spine, 24(21) (1999), pp. 2,229–33.