Current trends in limb lengthening:

No more rattling: biomechanical evaluation of a hexapod ring fixator free of play

Hexapod-ring-fixators have a characteristic rattling sound during load changes due to play in the hexapod struts. This play is perceived as unpleasant by patients and can lead to frame instability. Using slotted-ball-instead of universal-joints for the ring-strut connection could potentially resolve this problem. The purpose of the study was to clarify if the use of slotted-ball-joints reduces play and also fracture gap movement. A hexapod-fixator with slotted-ball-joints and aluminum struts (Ball-Al) was compared to universal-joint-fixators with either aluminum (Uni Al) or steel struts (Uni Steel). Six fixator frames each were loaded in tension, compression, torsion, bending and shear and mechanical performance was analyzed in terms of movement, stiffness and play. The slotted-ball-joint fixator was the only system without measurable axial play (<0.01 mm) compared to Uni-Al (1.2 ± 0.1) mm and Uni-Steel (0.6 ± 0.2) mm (p≤0.001). In both shear directions the Uni-Al had the largest play (p≤0.014). The resulting axial fracture gap movements were similar for the two aluminum frames and up to 25% smaller for the steel frame, mainly due to the highest stiffness found for the Uni-Steel in all loading scenarios (p≤0.036). However, the Uni-Steel construct was also up to 29% (450 g) heavier and had fewer usable mounting holes. In conclusion, the slotted-ball-joints of the Ball-Al fixator reduced play and minimized shear movement in the fracture while maintaining low weight of the construct. The heavier and stiffer Uni-Steel fixator compensates for existing play with a higher overall stiffness.

Management of complex femoral nonunion with monorail external fixator: A prospective study

AIM

To evaluate 30 patients who underwent distraction osteogenesis with monorail external fixator for complex femoral nonunion.

METHOD

Complex femoral nonunion includes infective non-union, gap nonunion, and limb-length discrepancy secondary to traumatic bone loss, which needs specialized treatment to ensure the functional integrity of femoral bone. 30 patients, including 28 male and 2 female (aged 22-62 years) patients, underwent surgical debridement followed by bone transport with monorail fixator. The lengthening index, radiographic consolidation index, functional status, bone healing, and various problems, obstacles, and complications encountered during the treatment were assessed.

RESULTS

Patients underwent a mean of 2.2 (range 1-4) surgeries before presentation. The mean bone defect after surgical debridement was 5.83 cm (range 2-16 cm). The mean treatment duration was 204.7 days (range 113-543 days). The mean lengthening index was 13.06 days/cm with range from 12 to 16 days/cm. Mean maturation index was 23.51 days/cm with range from 17 to 45.5 days/cm. In our study, bone result was excellent in 17, good in 9, fair in 3, and poor in 1 patient. In our study functional outcome is excellent in 9 [30%], good in 14 [46.67%], fair in 5, and poor in 2 patients. In our study, we encountered 34 problems, 17 obstacles, and 8 complications.

CONCLUSION

We concluded that monorail external fixator is an effective treatment option for complex nonunion femoral shaft fracture and its functional outcome is comparable with any other treatment options. Lack of complications and its effectiveness makes monorail external fixator the treatment of choice for complex nonunion femoral shaft.

Limb lengthening over plate

BACKGROUND

The limb lengthening over plate eliminates the associated risk of infection with limb lengthening over intramedullary nail. We present our experience of limb lengthening in 15 patients with a plate fixed on the proximal segment, followed by corticotomy and application of external fixator.

MATERIALS AND METHODS

15 patients (7 females, 8 males) were included in this consecutive series. The average age was 18.1 years (range 8-35 years). Fifteen tibiae and one femur were lengthened in 15 patients. Lengthening was achieved at 1 mm/day followed by distal segment fixation with three or four screws on reaching the target length.

RESULTS

The preoperative target length was successfully achieved in all patients at a mean of 4.1 cm (range 1.8-6.5 cm). The mean duration of external fixation was 75.3 days (range 33-116 days) with the mean external fixation index at 19.2 days/cm (range 10.0-38.3 days/cm). One patient suffered deep infection up to the plate, three patients had mild procurvatum deformities, and one patient developed mild tendo achilles contracture.

CONCLUSION

Lengthening over a plate allows early removal of external fixator and eliminates the risk of creating deep intramedullary infection as with lengthening over nail. Lengthening over plate is also applicable to children with open physis.

Clinical validation of the multiplier method for predicting limb length discrepancy and outcome of epiphysiodesis, part II

To validate the accuracy of the multiplier method in predicting limb length discrepancy (LLD) and outcome of epiphysiodesis, radiographs of 60 patients treated for LLD were measured. Data generated were used to predict maturity lengths of epiphysiodesed limbs, bone length discrepancies at maturity, and LLD at maturity after epiphysiodesis (residual discrepancy) using the multiplier and Moseley methods. The multiplier method mean error for bone length discrepancies predictions was 0.6 cm (SD = 0.6). Mean error for predicting lengths of epiphysiodesed limbs was 1.6 cm (SD = 1.2) for both methods. Mean errors for predicting residual discrepancies were 0.9 cm for the multiplier method using chronologic age, 1 cm for the multiplier method using skeletal age, and 1.3 cm for the Moseley method. Mean error difference between the methods was significant (P = 0.0008). The multiplier method accurately predicts LLD and outcome of epiphysiodesis and is more accurate than the Moseley method in predicting LLD at maturity after epiphysiodesis.