A biomechanical study on fixation stability with twin hook or lag screw in artificial cancellous bone.

The twin hook has been developed as an alternative to the conventional lag screw to be combined with a barrelled side-plate in the treatment of trochanteric hip fractures. With two oppositely directed apical hooks introduced into the subchondral bone of the femoral head, the twin hook provides different stabilising properties to the lag screw. The femoral head purchase of the twin hook and the lag screw were compared in a biomechanical study using artificial cancellous bone, and responses to axial and torsional loading was determined. A distinct yield point in load and torque was noted for the lag screw, representing failure of the laminas supporting the threads. For the twin hook, gradual increase of load and torque occurred during impaction of the bone supporting the hooks. The peak loads and torques were higher for the lag screw, but were similar for both devices after 8 mm deformation. The stiffness was higher for the lag screw, but in counter-clockwise rotation the stiffness for the lag screw was negligible. The twin hook appeared to provide fixation stability comparable to that offered by the lag screw, but with conceivable advantages in terms of a deformation response involving bone impaction and gradually increasing stability.

Femoral shortening in intertrochanteric fractures. A comparison between the Medoff sliding plate and the compression hip screw.

We compared 54 patients treated by a Medoff sliding plate (MSP) with 60 stabilised by a compression hip screw (CHS) in a prospective, randomised study of the management of intertrochanteric femoral fractures. Four months after the operation femoral shortening was determined from radiographs of both femora. In unstable fractures the mean femoral shortening was 15 mm with the MSP and 11 mm with the CHS (p = 0.03). A subgroup in which shortening was classified as large, comprising one-third of the patients in each group, had a similar extent of shortening, but more medialisation of the femoral shaft occurred in the CHS (26%) than in the MSP (12%) group (p = 0.03). Five postoperative failures of fixation occurred with the CHS and none with the MSP (p = 0.03). The marginally greater femoral shortening seen with the MSP compared with the CHS appeared to be justified by the improved control of impaction of the fracture. Biaxial dynamisation in unstable intertrochanteric fractures is a safe principle of treatment, which minimises the rate of postoperative failure of fixation.

Extramedullary fixation of 569 unstable intertrochanteric fractures: a randomized multicenter trial of the Medoff sliding plate versus three other screw-plate systems.

We compared the efficacy of the Medoff sliding plate (MSP) with 3 other screw-plate systems for fixation of unstable intertrochanteric fractures in a randomized multicenter trial of 569 elderly patients. The MSP has biaxial dynamic capacity along both the neck and the shaft of the femur unlike the other systems, which lack dynamic capacity along the shaft. 268 fractures were operated on with the MSP, and 301 with the dynamic hip screw (DHS), with or without a trochanteric stabilizing plate (DHS/TSP) or with the dynamic condylar screw (DCS). The MSP had recently been shown to the surgeons. The patients in the groups were similar as regards age, domestic situation, preinjury walking ability and type of fracture. We followed the patients clinically and radiographically for at least 1 year. There was no significant difference in walking ability at follow-up or rate of return to home. Fixation failure occurred in 18/268 fractures operated on with the MSP, in 8/238 with the DHS, in 3/49 with the DHS/TSP and in 1/14 with the DCS. The difference in the rate of fixation failure was not statistically significant when the MSP group was compared to the 3 other groups. In 14 of the 18 fixation failures in the MSP group, the biaxial dynamic capacity of the MSP had not been used due to technical errors by surgeons, unfamiliar with the new method. No selection bias was found regarding fracture types in the 2 subgroups of patients with correct or inadequate biaxial dynamization. Extramedullary fixation of unstable intertrochanteric fractures with these implants showed a low failure rate. When using the MSP, biaxial dynamization must be correctly performed.

Extracapsular hip fractures: fixation with a twin hook or a lag screw?

The twin hook, which has 2 oppositely directed apical hooks, is an alternative to the lag screw for use with a 'dynamic plate' in the fixation of trochanteric hip fractures. In this prospective study lasting 1 year, 102 consecutive patients with trochanteric hip fractures were treated by 19 surgeons with either a twin hook or a lag screw combined with a conventional sliding hip screw plate or a Medoff sliding plate. Seven intraoperative errors were made with the twin hook but postoperative migration did not differ significantly between the 2 groups. Postoperative fixation failures were equally distributed between the 2 groups. The twin hook provides adequate fixation, which is comparable to that produced by a lag screw.

Extramedullary fixation of 107 subtrochanteric fractures: a randomized multicenter trial of the Medoff sliding plate versus 3 other screw-plate systems.

We compared the efficacy of a load-sharing device, the Medoff sliding plate (MSP), with that of 3 other load-bearing screw-plate devices for the fixation of subtrochanteric fractures in a randomized multicenter trial of 107 elderly patients. 55 fractures were operated on with the MSP, and 52 with the dynamic hip screw (DHS) with or without a trochanteric stabilizing plate (TSP) or with the dynamic condylar screw (DCS). The patient material in the groups was similar regarding age, domestic situation, preinjury walking ability and fracture types. We followed the patients clinically and radiographically for a minimum of 1 year. There was no significant difference in walking ability or return rate to the home at follow-up. Fixation failure occurred in 1/55 fractures operated on with the MSP, in 3/32 with the DHS, in 3/12 with the DCS and in 2/8 with the DHS/TSR The difference in the rate of fixation failure was statistically significant, when the MSP group was compared to the 3 load-bearing devices in the other group (1 vs 8). On the basis of this experience, we think that the load-sharing principle of the MSP, which seems to facilitate fracture impaction and stability, appears to be a good alternative in extramedullary fixation of subtrochanteric fractures.

The Medoff sliding plate and a standard sliding hip screw for unstable intertrochanteric fractures: a mechanical comparison in cadaver femurs.

The Medoff sliding plate has a dual side capability along both the femoral shaft and neck to increase theoretically interfragmentary compression and load-sharing in hip fractures. We studied intertrochanteric fracture fixation in cadaveric bone to determine whether this device has a mechanical advantage over a standard sliding hip screw. 2-part and 4-part fractures were created in 12 cadaver femurs. The fractures were fixated and sequentially destabilized; bone and plate strains and fragment displacements were determined during testing, as a function of applied physiological loads before and after short-term cycling. The Medoff sliding plate imposed a higher mean medial cortex strain than the sliding hip screw in all fracture models and at all loading levels, and the difference was statistically significant in the 2-part and in the unstable 4-part fracture models. The loading of the medial cortex region after cycling was approximately 50% higher in the Medoff samples than in the sliding hip screw samples. There were no significant differences in plate strains, fracture displacements or load to failure between the 2 devices. These observations favor the dual sliding principle as regards providing fracture compression and load-sharing, which may explain low failure rates in clinical series of unstable intertrochanteric fractures, treated with the Medoff sliding plate.

Different ways to treat subtrochanteric fractures with the Medoff sliding plate.

Thirty-two consecutive subtrochanteric fractures in 32 patients were stabilized using the Medoff sliding plate and were followed up prospectively for 1 year. Two patients died during the first postoperative year. Twenty-nine of the remaining 30 (97%) fractures united by 1-year followup. Two types of plate dynamization schema were used: uniaxial (17 patients) and biaxial (15 patients). With uniaxial dynamization, plate sliding averaged 12 mm along the femoral shaft without medialization of the femoral shaft. With biaxial dynamization along the femoral shaft and the neck, plate sliding averaged 11 mm and screw in barrel sliding averaged 9 mm; medialization of the femoral shaft ranged from 0% to 35% of the femoral shaft diameter. Three fractures treated with uniaxial dynamization had migration of the lag screw within the femoral head; all three fractures united without additional screw migration after secondary or staged biaxial plate dynamization.

Intramedullary versus extramedullary fixation of subtrochanteric fractures. A biomechanical study.

We compared two different subtrochanteric fracture fixation techniques, an intramedullary hip screw system (IMHS) and an extramedullary, dual sliding screw-plate system (MSP), to determine relative fixation stability. 6 matched pairs of osteosynthesized osteopenic cadaver femurs were axially loaded to 1000 N with concurrent, simulated abductor forces of 0%, 50%, or 86% of the applied head force. The initial loading sequence was made with uniaxial dynamization--the lag screw of the MSP locked and distal locking of the IMHS nail. Femoral head displacement and medial femoral strain were measured for intact femur controls, after fixation of a 2-part reverse oblique subtrochanteric fracture and finally a 3-part reverse oblique subtrochanteric fracture with a lateral wedge defect. The samples were then loaded at 750 N for 10(4) cycles with both devices uniaxially locked, followed by 10(4) cycles with both devices fully biaxially dynamized (unlocked). For the 2-part subtrochanteric fracture pattern, both devices exhibited similar inferior displacements of the femoral head (average 2.0 mm) and medial femoral strain (approximately 70% of intact). Increasing abductor forces decreased medial compressive strain but did not significantly affect head displacement. For the 3-part fracture model, the MSP demonstrated significantly less inferior displacement of the head (1.6 mm vs. 2.1 mm) and both devices demonstrated significantly decreased medial strain. After cycling, head displacement increased approximately 50% in both devices and medial strain increased slightly. After unlocking and cycling, the MSP group showed significant lateral displacement of the proximal fragment. The IMHS and MSP devices provide similar stability for fixation of 2-part and 3-part reverse oblique subtrochanteric fractures. In a biaxially dynamized, 3-part reverse oblique fracture, displacement of the proximal fragment can occur with the MSP.

A new radiographic method for evaluating the degree of sliding in devices used in hip-fracture surgery.

PURPOSE: To find a practical method for estimating the degree of sliding that occurs in screw-plate devices used in hip-fracture surgery. Greater understanding of the sliding mechanisms in different fracture types should improve surgical technique and reduce the failure rate. METHODS AND RESULTS: In dynamic screw-plate devices, the lag screw slides inside the barrel of the plate. A recent innovation allows the barrel-plate to slide inside a side-plate, thus making possible a combined fracture compression along the neck and the shaft of femur. The lengths of the different parts and the angle of a device in vivo, measured on a radiograph, depend on the position of the femur relative to the photographic film and the roentgen source. We obtained these measurements with a ruler and a protractor from sequential a.p. radiographs of the hip and implemented them in a special computerized program that used the principles of the scaled orthographic and the central projection models. These calculations provided the correct amount of sliding by the lag screw and by the barrel-plate within the side-plate. CONCLUSION: The method presented here can establish the real degree of sliding in screw-plate devices from standard a.p. radiographs independently of the position of the hip.

Biaxial dynamization in unstable intertrochanteric fractures. Good experience with a simplified Medoff sliding plate in 94 patients.

In a prospective study, 94 consecutive patients with unstable intertrochanteric fractures were treated by 16 surgeons, using a modified 4-hole Medoff sliding plate and followed clinically and radiographically for 1 year. Weight bearing after surgery was allowed as tolerated. This new device is smaller and uses a simpler technique of insertion than the original 6-hole Medoff sliding plate. The modification of the plate makes biaxial sliding along both the shaft and the neck of the femur obligatory. All fractures united and no postoperative lag screw penetration occurred. The use of a shorter side-plate with 4 cortical bone screws was sufficient for fixation and no plate loosening or breakage was observed. On the basis of this experience, biaxial dynamization seems to facilitate fracture impaction and stability, and the simplified 4-hole Medoff sliding plate appears to be a suitable method for the treatment of unstable intertrochanteric fractures.

Use of the Medoff sliding plate for subtrochanteric hip fractures.

OBJECTIVE: To evaluate the effects of dynamization of a sliding hip screw plate on the fixation stability for several types of subtrochanteric fractures. Clinical results of treating reverse oblique fractures occasionally show medialization of the femoral shaft. DESIGN: Two types of plate dynamization were compared using the same test protocol in identically prepared groups of uniform, artificial femurs. METHODS: Sawbones composite femurs (Pacific Research Labs, Vashon, WA) having five orientations of simulated subtrochanteric fractures were used with the Medoff plate (Medpac, Inc., Valencia, CA) either fully dynamized or with the sliding lag screw locked. These specimens were physiologically loaded and cycled and displacements of the proximal femur determined. RESULTS: Significantly more shaft medialization occurred with reverse oblique fracture patterns when the Medoff plate was fully dynamized. CONCLUSION: Clinical treatment of reverse oblique fractures with the Medoff plate should be performed using the lag screw locked and only the plate dynamized.

Two-way compression along the shaft and the neck of the femur with the Medoff sliding plate: one-year follow-up of 108 intertrochanteric fractures.

The Medoff sliding plate (MSP) is a new device used to treat intertrochanteric and subtrochanteric fractures. There are three options for sliding; either along the shaft or the neck of the femur, or a combination of both. In a prospective series of 108 consecutive displaced intertrochanteric fractures we used combined dynamic compression. The patients were followed clinically and radiologically for one year. All fractures healed during the follow-up period. The only postoperative technical failure was one lag-screw penetration. Combined compression of the MSP gives increased dynamic capacity which reduces the risk of complications. The low rate of technical failure in our series compares favourably with that of the sliding hip screw or the Gamma nail but randomised trials comparing the MSP with other hip screw systems are necessary to find the true role of the MSP with its various sliding modes.

One-way compression along the femoral shaft with the Medoff sliding plate. The first European experience of 104 intertrochanteric fractures with a 1-year follow-up.

This is an assessment of a new device for treatment of intertrochanteric and subtrochanteric fractures. The Medoff sliding plate (MSP) allows compression in 3 different modes: along the femoral shaft, along the femoral neck or a combination of both. In this prospective series of 104 consecutive intertrochanteric fractures, dynamic compression was allowed only along the femoral shaft. Simple undislocated intertrochanteric 2-part fractures were excluded. The patients were followed clinically and radiographically for 1 year. 21 patients died within 1 year after the operation. 7 technical failures including 2 non-unions occurred. All were lag screw penetrations, 4 of which were considered to be due to unforced errors by the surgeons. The technical failure rate in this preliminary evaluation of the MSP is similar to that of the dynamic hip screw. Randomized trials comparing the MSP with other hip screw systems should follow to ascertain possible advantages of the MSP, with its various sliding modes in different types of fractures of the proximal femur.

Predicting results of rehabilitation after hip fracture. A ten-year follow-up study.

Data influencing the outcome of rehabilitation after hip fracture were obtained from 103 consecutive patients. All were admitted from their own homes and were observed at the time of discharge from the hospital and at three weeks, four months, one year, five years, and ten years postfracture. Background and functional variables were recorded and analyzed by means of multivariate discriminant statistical techniques. The three most important variables for discharge to home were (1) the ability to walk two weeks after surgery, (2) living with someone, and (3) good general health. From four months until ten years postfracture, the most persistent positive variable for returning to and living at home was an active prefracture lifestyle. The most persistent negative variable was old age. By means of prognostic schemes, it is possible, as early as the time of fracture or a few days after surgery, to make a reliable prediction as to whether the patient will return home. Both the patient and society benefit from early rehabilitation at home in cooperation with primary care personnel and social workers, as it reduces the cost of the injury by avoiding a lengthy hospital stay and unnecessary institutional aftercare.

Function and social status 10 years after hip fracture. Prospective follow-up of 103 patients.

Function and social outcome for 103 consecutive patients, mean age 75 years, admitted from their own homes after a hip fracture were studied during a 10-year period. Within 4 months after the fracture, 81 patients had returned home, and the percentage of survivors living at home from then on was then fairly constant. At 10 years after fracture, 31 patients were living at home, 6 were in institutions, and 66 were dead. ADL, walking ability, and household activities remained at the level already achieved within 4 months after fracture during the 10-year period. The need for social services help did not increase; about one third of the survivors had communal home help throughout the 10-year period. Patients who before fracture were healthy and living with someone and within 2 weeks after the fracture could walk with a four-legged aid or better had a good prognosis for living in their own home. The hip fracture did not effect their subsequent fate.

Hip fracture incidence in Lund, Sweden, 1966-1986.

The hip fracture incidence in the city of Lund and its rural surroundings was studied for the years 1966, 1972, 1981, and 1986. The total incidence increased from 3.3 to 5.1 per 1,000 inhabitants above 50 years of age. For persons more than 80 years old, the incidence almost doubled from 13.2 to 25.5, i.e., this group represented the entire increase in incidence. In the urban population, men with cervical fractures had an increased incidence. A smaller increase in incidence for both men and women was found in the rural area. Compared with larger cities, the incidence increase in the urban population in Lund was lower over time, but in 1986 the figures were comparable to those in Gothenburg in 1981. The total incidence in the mixed urban and rural population was as of 1981 higher than in Denmark and Finland, but lower than in Norway. If the incidence in the elderly continues to increase to 1995, there will be three times as many hip fractures as there were in 1966.

Effects of strategy changes in the treatment of femoral neck fractures during a 17-year period.

From 1966 to 1982 new concepts in the treatment of fresh femoral neck fractures were introduced at a university hospital in Sweden. These included immediate postoperative weight-bearing, a program with rehabilitation at home in collaboration with primary care, and an alteration of the treatment policy from primary hemiarthroplasty to a flanged nail and finally to hook pins. The total annual number of hospital days was reduced by about one-third during this period in spite of the fact that the annual number of femoral neck fractures doubled. Thus, the mean hospitalization time decreased from 44 to 16 days. The proportion of patients admitted from their own homes decreased from 80% to 52% during the 17-year period, and for these, the return rate home at discharge from the hospital increased from 44% to 75%. According to several reports from Scandinavia, the number of hip fractures will double in the next two decades. Ways of further reducing the hospitalization time, new techniques, and, if possible, methods of preventing hip fractures must be sought.