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. 2020 Oct 2;21(1):646.
doi: 10.1186/s12891-020-03674-8.

Restoring global offset and lower limb length with a 3 offset option double-tapered stem

Stefano Biggi  1   2 , Lorenzo Banci  3 , Riccardo Tedino  4   5 , Andrea Capuzzo  4   5 , Gabriele Cattaneo  4   5 , Stefano Tornago  5 , Andrea Camera  4   5
Affiliations

Restoring global offset and lower limb length with a 3 offset option double-tapered stem

Stefano Biggi et al. BMC Musculoskelet Disord. .

Abstract

Background: A proper restoration of hip biomechanics is fundamental to achieve satisfactory outcomes after total hip arthroplasty (THA). A global hip offset (GO) postoperatively reduction of more than 5 mm was known to impair hip functionality after THA. This study aimed to verify the restoration of the GO radiographic parameter after primary THA by the use of a cementless femoral stem available in three different offset options without length changing.

Methods: From a consecutive series of 201 patients (201 hips) underwent primary cementless THA in our center with a minimum 3-year follow up, 80 patients (80 hips) were available for complete radiographic evaluation for GO and limb length (LL) and clinical evaluation with Harris hip score (HHS). All patients received the same femoral stem with three different offset options (option A with - 5 mm offset, option B and option C with + 5 mm offset, constant for each sizes) without changing stem length.

Results: Mean GO significantly increased by + 3 mm (P < 0.05) and mean LL significantly decreased by + 5 mm (P < 0.05) after surgery, meaning that postoperatively the limb length of the operated side increased by + 5 mm. HHS significantly improved from 56.3 points preoperatively to 95.8 postoperatively (P < 0.001). Offset option A was used in 1 hip (1%), B in 59 hips (74%) and C in 20 hips (25%).

Conclusions: The femur is lateralized with a mean of + 5 mm after surgery than, the native anatomy, whatever type of stem was used. Thus, the use of this 3-offset options femoral stem is effective in restoring the native biomechanical hip parameters as GO, even if 2 offset options were considered sufficient to restore GO.

Keywords: Global offset; Hip parameters; Leg length; Offset; Total hip Arthroplasty.

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Conflict of interest statement

LB is employed as Clinical Affairs Manager by Permedica S.p.A., Via Como 38, 23807, Merate (LC), Italy. The other authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
The Synthesis femoral stem (Permedica S.p.A., Merate, Italy) investigated in the study. The Synthesis stem is a cementless, sandblasted, double-tapered, straight, CLS Spotorno-like design. The Synthesis stem has three different offset options (offset A, B and C) which do not change the stem length. Offset B stem has 0 mm offset and 131° CCD angle. Offset A stem has −5 mm offset and 136° CCD angle. Offset C stem has + 5 mm offset and 127° CCD angle. The offset is constant for each stem size
Fig. 2
Fig. 2
Measurements of the hip biomechanical radiographic parameters by using Horos Viewer software for MAC at preoperative (a) and follow-up time (b). The global hip offset (GO) was defined by the sum of the femoral offset (FO) and the acetabular offset (AO). Limb length (LL) was defined as the distance between the medial apex of the ipsilateral lesser trochanter and the line passing through the lower margins of the ischial tuberosity
See this image and copyright information in PMC

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